This invention relates to transferring information or data from a data transmitter including a cathode ray tube (CRT), such as a computer having a CRT monitor, to a portable information device (e.g., a wrist instrument, such as a multi-function electronic wristwatch), and more particularly to synchronizing the rate of data transfer from transmitter to receiver.
The use of both computers and hand-sized, portable information devices continues to expand. Various methods have been developed for transferring information between computer processors (e.g., both synchronous and asynchronous serial communication devices), using communications interface conventions such as RS232C, RS449A and V.35. The binary coded signals may be transmitted in standard codes such as ASCII, EBCDIC, with established protocols providing for handshake procedures, starting, stopping and checking the data transmitted. Most of the systems for establishing communication links are designed for two-way transmission.
There are several ways to use optical technology for transferring information. One implementation of optical technology utilizes a combination of optical emitters and photosensors to transfer information. Typically, hardware is dedicated specifically to both devices of the transfer process to insure that the receiver and transmitter are set to operate at the same transmission rate or baud rate. The device to be loaded with information is placed in front of the emitters and the information transfer is started. Unfortunately, this method of information transfer also requires specialized hardware and is often not compatible with existing hardware installations.
As the use of portable information devices expands, there is an increasing need for such devices to be flexible in their functionality. Many existing portable devices have been designed for multiple functions, such as a combination watch/calculator. Wrist instruments have expanded from their time keeping role to include: databanking, chronometer, alarm, computation, odometer, paging, and communication functions. A disadvantage of many existing portable information devices is that they cannot easily be downloaded with programs providing new functionality. A further disadvantage of many existing portable information devices is that their databases cannot be easily updated without manually entering new data. The existing devices that can be updated typically have very limited input capabilities because they either have no keyboards at all or very rudimentary keyboards, or else they require that the updating occur from specific hardware. This severely limits the user's flexibility because the user must have easy access to updating hardware, which will most likely not be portable. Wristwatches in particular are difficult for entry of information or updating information. Various schemes have been proposed for entry of data using pushbuttons or tiny keyboards, none of which have been entirely satisfactory. An optimum configuration would be one where the portable device could be updated from any controllable light source such as a CRT video display screen found in desk size computer monitors and television sets.
A system has been proposed in co-pending U.S. patent application Ser. No. 08/155,326 filed in the names of Michael Jacobs and Mark Insero on Nov. 22, 1993 (now U.S. Pat. No. 5,488,571) and assigned to the present assignee. This application describes a system for transferring data from a CRT video display monitor on a personal computer to a portable information device such as a multifunction electronic wristwatch. The CRT video display has a video signal generator providing raster scanning of the screen and a program for formatting the binary coded data into blocks of serial data bits, with start bit and stop bit. The blocks of data are supplied to the video signal generator in synchronism with raster scanning of the screen so as to provide an integral number of one or more blocks of data for each vertical frame, and modulated to vary the brightness of the screen and provide light pulses which are seen by the operator as the presence or absence of horizontal spaced lines or line segments on the CRT corresponding to presence or absence of binary coded transmitter pulses. The portable information device is manipulated within line of sight of the CRT screen and has a photosensor to detect light pulses when the photosensor is directed toward the screen. Signals from the photosensor are amplified and filtered to remove ambient light source flicker and extraneous spurious light signals and to convert the receiver pulses to binary coded data blocks varying between high and low logic levels at a preselected pulse reception rate. The portable information device stores the received data for further use. Transmission of data is only in one direction--from CRT to the portable information device, which is not designed to send information back to the CRT.
One problem in such a system concerns a portable information device which is designed to receive data at a fixed or pre-defined data rate or baud rate, but which may need to receive data from CRT monitors having different vertical frame rates, different internal timing and different numbers of horizontal scan lines in each frame. Therefore if the portable information device is designed to accept data transfer at 2400 baud and light pulses are being emitted from the CRT at 2000 baud or 3000 baud, the data will be garbled and not received correctly. While a computer may be programmed so that it causes light pulses to be emitted at 2400 baud for correct reception, the program is designed for a monitor with known characteristics. Changing monitors or changing computers may render the data which is transferred to be unintelligible.
Accordingly, one object of the present invention is to provide an improved apparatus for synchronizing data transfer rate from a CRT video monitor to a portable information device.
Another object of the invention is to provide a portable information device with a photosensor which facilitates calibration of a PC with a CRT video monitor so that it matches the data receiving capability of the portable information device.
Another object of the invention is to provide an improved calibration process and program which facilitates calibration of a PC with a CRT video monitor so that it matches the data receiving capability of a portable information device, with a photosensor.